1. Field of the Invention
This invention relates to a rotary valve mechanism for improving part-load fuel efficiency of automobile and other throttled, spark ignition internal combustion engines of both the two stroke and four stroke cycle types by minimizing the pumping losses or negative work even below the corresponding loss levels in compression ignition or "diesel" engines. It corresponds in the steam engine field to the introduction of the Stephenson variable inlet cut-off valve.
2. Description of the Prior Art
Throttled spark-ignition internal combustion engine technology is well known in the art and of course is extremely popular and most familar to the average person as the power source of conventional automobiles and like vehicles. However, in the operation of the internal combustion engine, one of the most complex components or sub-assemblies in such an engine, particularly in automotive applications, is the carburetor.
In an automobile engine of the internal combustion type, the carburetor throttle is adjusted by the driver, through manipulation of the accelerator pedal, to a position which gives the desired power output. This throttling drops the engine intake pressure below atmospheric level thereby decreasing the engine performance to the required value. After the combustion process is completed in the various cylinders of the engine, the exhaust must be pumped out of such cylinders against atmospheric pressure. This in turn of course requires work to be expended to accomplish the flow of such exhaust against the existing atmospheric pressure on the exterior of the combustion cylinders. The pressure energy lost by the carburetor restriction must be replaced by work which would otherwise be available as useful power output at the flywheel if such energy were not required in exhausting the combustion cylinders. The above problems of course do not apply to diesel type engines which have no air throttle and therefore do not have this flow-work loss to reduce their efficiency.
However, generally such diesel type engines while commonly used in automobiles and like vehicles are inherently much more expensive and have reduced performance characteristics compacted to conventional spark ignition internal combustion engines. They must compress the air charge to high pressures and to ignition temperature whether at full load or at idling conditions.
To overcome the problem of throttling resulting in pumping losses or negative work while exhausting the cylinders, devices or assemblies exist in the prior art which are directed specifically to this problem. Particularly the U.S. Pat. No. 3,203,409 to Allen shows an apparatus for controlling the air taken into the combustion chamber of an I.C. engine through the use of a rotary valve. The rotation of the rotary valve is varied relative to the rotation of the crank shaft through the provision of a differential gear box. This differential gear box is placed in driving relation to the driving axle shaft of the various rotary valves associated with each of the cylinders. Physical manipulation of a lever varies the operational position of the gears within the differential gear box thereby causing a change in the relative rotation of the individual rotary valves and the crank shaft, dependent upon the power demands of the engine. While possibly operable, the specific mechanism and operational characteristics of Allen through the provision of the gear box assembly, valve axle and relatively large diameter rotor, etc. seem overly complex as well as providing questionable operating characteristics for a practical application.
Accordingly, there is a need to solve the throttling problem associated with spark-ignition type I. C. engines particularly in automotive uses. It is acknowledged that similar savings could be produced by separately programming the operating characteristics of the present poppet intake valves or ports of the engine. However, the cost and complexity of such an operation would be prohibitively great. Since it is also well recognized that the I. C. engine particularly for automotive uses, seldom operates at a full load capacity, considerable improvement in average fuel economy could be accomplished by operating the spark-ignition engine at only the indicated mean effective pressures required to maintain the capacity desired. The resulting savings in pumping loss would thus be maximum at low speeds and low loads and would of course be decreased to zero at full load conditions.
Such a structural modification of spark-ignition engines similar to "and-gating" in electronics should be dependable in operation, less costly to produce, and require less modification to the present basic engine designs than prior art known methods and should accomplish the same effect as programming of the operations of the poppet or port type intake valves with much less cost involved.